Bent glass is used extensively for vehicle side and rear windows and also for vehicle lights. Such bent glass is also frequently tempered so that the glass not only has an aesthetically appealing shape that compliments the design of the vehicle, but also provides a good resistance to breakage.
In order to perform such bending, the glass sheet must be heated to its deformation point of about 1,200.degree. to 1,300.degree. F. and then bent to the required shape. If tempering is desired the bent glass sheet is typically rapidly cooled by an air spray. Various United States patents disclose apparatus for bending and tempering glass sheets with press benders having shaped surfaces between which heated glass is clamped to shape it prior to being air cooled by a quench unit. For example, U.S. Pat. Nos. 3,454,389; 3,476,542; 3,488,178; 3,600,150; and 3,951,634 disclose such press bending and tempering apparatus.
Other United States patents disclose apparatus for heating glass sheets prior to bending and tempering thereof on fluid support beds as the glass is conveyed through the furnace. Such apparatus is disclosed in the U.S. Pat. Nos. 3,497,340, 3,607,187 and 3,607,200. Normally the support bed is inclined slightly with respect to the horizontal so that gravity engages an edge of the glass with a movable frame that provides the impetus for glass movement along the bed. There is no contact between the bed and the oppositely facing surfaces of the glass during the conveyance as the glass is heated. This lack of contact prevents marring and scratching of the soft surfaces of the glass as the glass reaches its deformation temperature. However, there is normally mechanical contact with the glass during the bending after the heating in preparation for a cooling quench that tempers the glass in its bent condition.
Vacuum forming of heated glass sheets is disclosed by U.S. Pat. No. 3,778,244 wherein the sheet glass is first heated during conveyance along a roller hearth conveyor. After heating a lifter with a curved downwardly facing surface has a vacuum applied thereto along the surface to shape the glass. After shaping against the curved surface of the lifter the vacuum is terminated to drop the glass onto a mold for conveyance to a waiting operator who removes the glass from the mold.
U.S. Pat. Nos. 4,282,026 and 4,297,118 discloses an apparatus for conveying sheet glass along a substantially horizontal path which extends through a tunnel-type furnace where a series of sheets are heated to the deformation temperature of the glass and along an extension of the path into a shaping station where each glass sheet is in turn transferred onto a vacuum mold. The vacuum mold lifts and holds the heat-softened glass sheet by suction. At about the same time a carrier mold ring, having an outline shape conforming to that desired for the glass sheet moves into a position below the vacuum mold. Release of the vacuum deposits the glass sheet onto the tempering ring. The tempering ring supports the glass sheet while it conveys the glass sheet into a cooling station for rapid cooling.
In the U.S. Pat. No. 4,282,026 vertical movement of the vacuum holder or, alternatively, auxiliary lifters positioned between the conveyor rolls lifts the sheet of glass upwardly in spaced relationship to the conveyor rolls.
In the U.S. Pat. No. 4,297,118 the apparatus includes an upper vacuum mold which first engages and lifts a heat-softened glass sheet by suction which provides clearance for a shaping and tempering ring to enter the shaping station. The vacuum mold is thereafter moved outside the furnace during successive bending operations.
The U.S. Pat. No. 3,607,187 discloses a vacuum mold which lifts softened glass sheets by first being lowered toward the sheet and applying suction through a downwardly facing permanently curved shaping surface. The vacuum mold is thereafter moved horizontally over the conveyor belt from the shaping station beyond an enclosed heating furnace to a cooling station. The mold redeposits the glass sheet onto a conveyor belt at a cooling station.